Silicone Surfactants Research Articles

Effect of headgroups on the aggregation behavior of cationic silicone surfactants in aqueous solution

Three cationic silicone surfactants, 1-methyl-3-[tri-(trimethylsiloxy)]silylpropyl-imidazolium chloride (Si4mimCl), (2-hydroxyethyl)-N,N-dimethyl-3-[tri-(trimethylsiloxy)]silylpropylammonium chloride (Si4mam-OHCl), 1-methyl-1-[tri-(trimethylsiloxy)]silylpropylpyrrolidinium chloride (Si4pyCl), with the same hydrophobic group and different headgroups were synthesized. Their aggregation behavior in aqueous solution was systematically investigated by surface tension, electrical conductivity, and steady-state fluorescence. Surface tension of water can be reduced almost to 20mNm−1 with the addition of the cationic silicone surfactants. This result indicates that all the three surfactants exhibit remarkable surface activity. Because of the effect of the headgroups, the critical micelle concentrations (CMC) values increase following the order Si4pyCl<Si4mimCl<Si4mam-OHCl, and Si4pyCl packs more tightly at the air/water interface compared with Si4mimCl and Si4mam-OHCl. Electrical conductivity measurements show that all the three cationic silicone surfactants have low degree of counterion binding (β) and the β values for Si4pyCl and Si4mam-OHCl increase with increasing the temperature in the investigated temperature range. Thermodynamic parameters (ΔHm0, ΔSm0, and ΔGm0) of micellization indicate that the micellization for Si4mimCl in aqueous is enthalpy-driven, and that for both the Si4pyCl and Si4mam-OHCl entropy-driven.

Controllable synthesis of silica hollow spheres by vesicle templating of silicone surfactants

Silica hollow spheres (SHSs) have been designed and prepared through three distinct synthetic routes based on the self-assembling of comb-like copolymer silicone surfactants. This process was based on the rule of similarities for hydrophobicity and hydrophilicity between the surfactant and a silica source. The directed silica wall formations were performed at different confined spaces of the vesicles, including the outer and inner surfaces, and the hydrophobic parts of the bi-layers. The resultant SHSs possess tailorable shell thicknesses (20–400 nm), particle sizes (200 nm–1.2 μm), and a high dispersibility in aqueous solutions.

Effect of t-octylphenoxylpolyethoxyethanol (TX-100) on the dilute aqueous solution phase diagrams, surface activity and micellization behavior of non-ionic silicone surfactants (SS) in aqueous media

Dilute aqueous solution phase diagrams, surface tension, dynamic light scattering (DLS) and dilute solution viscosity measurements have been made in aqueous solutions of nonionic silicone surfactants (SS) in presence of t-octylphenoxylpolyethoxyethanol (TX-100). Critical micelle concentration, thermodynamic parameters of association, interfacial characteristics such as pC20, surface excess, Γmax , area per adsorbed molecule, a1s along with the size and shape and intrinsic viscosities of the associates have been determined and discussed to ascertain the effect of TX-100 as an additive in SS aqueous solutions. The importance of hydrophobic/hydrophilic (hp/hl) ratio of the SS rather than their molecular architecture and molar mass on their overall interaction with TX-100 micelles has been reflected in the above parameters for the mixture solutions. It was observed that the mixed species in SS aqueous solutions in TX-100 are more hydrophilic in nature and the overall association process in the mixture solutions is entropy driven. TX-100 addition to SS micellar solutions induces the dissociation of SS micelles. As compared to the room temperature, the mixed micelles at elevated temperatures were large in size suggesting that the ellipsoidal micelles in mixed state grow along their major axis that is typically characteristic of the micelles of the individual nonionic SS or TX-100 surfactants at temperatures close to the turbid point.

Interpenetrating polymer networks templated on bicontinuous microemulsions containing silicone oil, methacrylic acid, and hydroxyethyl methacrylate

Polydimethylsiloxane-poly(methacrylic acid—hydroxyethyl methacrylate) interpenetrating polymer networks (PDMS-P(MAA–HEMA) IPN) were formulated and polymerized simultaneously from bicontinuous microemulsion templates. Microemulsions containing reactive silicone oils and MAA/HEMA in aqueous solution were stabilized with silicone surfactants, and were then reacted at 50 °C for 3 h under an N2 atmosphere. The formation of bicontinuous morphology was confirmed by laser scanning confocal microscopy, reversible swelling behavior, differential scanning calorimetry, texture analysis, and permeability to vitamin B12 in aqueous solution. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization, yielding a more uniform IPN morphology with domain sizes of <200 nm at equilibrium swelling. The process developed here demonstrates a simple, single-step polymerization approach to forming IPNs from low viscosity microemulsion templates, and could potentially be extended to a variety of hydrophilic and hydrophobic monomers.

Aggregation behavior of silicone surfactants in ethylammonium nitrate ionic liquid

The aggregation behavior of two silicone surfactants (monomeric and Gemini) was studied by surface tension measurements in a room temperature ionic liquid, ethylammonium nitrate (EAN), at various temperatures. A series of parameters, including critical micelle concentration (CMC), surface tension at the CMC (γ CMC), adsorption efficiency (pC 20), and effectiveness of surface tension reduction (Π CMC), were obtained. By comparing the silicone surfactants with traditional surfactants, we deduced that the surface activity of the silicone surfactants in EAN was superior to the activity of other surfactants. In addition, from the CMC values and their temperature dependence, we estimated the thermodynamic parameters of the micelle formation, $$ \Delta G_m^0 $$ , $$ \Delta H_m^0 $$ , and $$ \Delta S_m^0 $$ . It was revealed that the micellization of the silicone surfactants is entropy driven at low temperature and enthalpy driven at high temperature. Isothermal titration calorimetry measurements were also carried out to study the micellization of Gemini silicone surfactant. 1H NMR was performed to study the silicone surfactant micelle formation mechanism in EAN.

The Performance of Polyether Modified Polysiloxane

According to the corresponding national standard methods, the surface tension, HLB value, CMC value and emulsification performance of the product were determined. Compare the hydrolytic stability with other three kinds of organic silicon surfactants, the experiment result shows that the hydrolytic stability of product is better than the similar products. The key to reduce the hydrolysis rate of polyether modified polysiloxane surfactant is to reduce the contact of polysiloxane chain in surfactant molecules with water solution. For methoxy-terminated polyether modified polysiloxane, the methyl ether open as the umbrella, which can reduce the contact of polysiloxane chain in surfactant molecules and water solution to a certain extent, so the hydrolysis stability raise.

Hydration-induced reinforcement of rigid polyurethane–cement foams: mechanical and functional properties

Mechanical and functional properties of a newly proposed hybrid foam based on rigid polyurethane foam and Portland cement for application in the building field are herein reported. The hybrid is characterized by the co-continuity of the two phases, hydrated cement and polyurethane, which cooperate in a synergistic way to the properties of the resulting material. Furthermore, the closed-cell foam structure gives the material properties typical of porous materials: in particular, the hybrid foam evidences thermal insulation, sound absorption and acoustic insulation, high impact energy and low density typical of polymeric foams. At the same time, the hybrid foam exhibits water vapor permeability, improvement of thermal stability, high compressive mechanical behavior, and adhesion to concrete and mortars typical of inorganic binders such as cement. The materials were obtained by mixing cement powder with polyurethane foam precursors, i.e., methylene di(phenyl-isocyanate), polyol polyether and catalysts, and silicone surfactants. Water was used as blowing reagent. The resulting compounds were foamed in flat closed molds. The cement phase was then allowed to hydrate in accelerated conditions, i.e., in water at 60 °C for 72 h. Mechanical, morphological, and functional characterization showed that the hydrated cement particles interacted with each other, forming an inorganic network within the polymeric matrix (co-continuity), thus “hydration-induced reinforcement of polymer–cement” hybrid foam, in contraposition with the term “composite foam.”

Comparison of the influence of fluorocarbon and hydrocarbon surfactants on the adsorptions of SDS, DTAB and C12E8 at the air/water interface by MD simulation

Adsorptions of sodium dodecylsulfate (SDS), dodecyltrimethylammonium bromide (DTAB) and octaethylene glycol monododecyl ether (C12E8) at the air/water interface in the presence of hydrocarbon and fluorocarbon surfactants (HCEP and FCEP) were investigated by molecular dynamics (MD) simulation. With the addition of HCEP or FCEP, the monolayer is more organized than in individual surfactant systems. Extremely expanded C12E8 chain in a smaller tilt angle is discovered in C12E8/HCEP system. In SDS or DTAB systems, relatively small tilt angle of surfactants is observed in the presence of FCEP. Their analog, a silicone surfactant DSEP shows a favorable effect on interfacial properties with DTAB.

ABC copolymer silicone surfactant templating for biomimetic silicification

Using the ABC copolymer silicone surfactant polydimethylsiloxane (PDMS)-graft-(polyethylene oxide (PEO)-block-propylene oxide (PPO)) (PSEP, Scheme 1a) as a template and tetraethoxysilane (TEOS) as a silica source, silica particles with various structures and morphologies (i.e., disordered spherical micellar aggregation, two-dimensional p6mm mesostructure, asymmetric multi-layer non-equilibrium vesicles and symmetric monolayer vesicles) were synthesized by changing the synthesis temperature from 30 to 80°C. Increasing the hydrophobicity of the surfactant by increasing the temperature resulted in an increase in the surfactant packing parameter g, which led to the mesophase transformation from micellar to cylinder and later to a lamellar structure. The good compatibility between the PDMS and the TEOS, the different natures of the hydrophobic PDMS and PPO segments, and the hydrolysis and condensation rates of TEOS enabled the variation of silicification structures. This novel silicone surfactant templating route and a new type of materials with highly ordered mesostructures and asymmetric morphologies provide a new insight into the molecular factors governing inorganic–organic mesophase and biosilicification for fabricating functionalized materials.

Experimental research and DPD simulation on the interaction between an ethoxy-modified trisiloxane and F127

The interactions between surfactants and polymers are widely investigated due to favorable changes on properties in their mixtures. Silicone surfactants and pluronic copolymers, both having low toxicity, are used in the detergent, cosmetics, medical, and pharmaceutical fields. Their mixture may gain better performance in their further applications. Therefore, we investigated the interaction between an ethoxy-modified trisiloxane (a silicone surfactant named Ag-64) and a block polyether F127 in this paper. From aggregation behavior of Ag-64 and F127, the formation mechanism and conformation of the aggregates were proposed based on experiments and dissipative particle dynamics (DPD) simulation. The surface activity and aggregation behavior of Ag-64 are affected by F127 in aqueous solutions. As the amounts of added Ag-64 increase, two types of aggregates (Ag-64/F127 aggregate with F127 as skeleton and the “pearl- necklace” aggregate in which Ag-64 micelles are strung along F127 chain) form successively. At higher polymer concentration, F127 twists together to form a coil/cluster aggregate with Ag-64. The results of DPD simulation approve that two main factors, the hydrophobic association and twist of F127 coil, contribute to the formation of different aggregates of Ag-64 and F127.

Small Angle Neutron Scattering and Viscosity Measurements on Silicone, Ionic, and Nonionic Surfactant Mixed Systems in Aqueous Solutions

The structural features of mixed micelles of a silicone surfactant (SS-1) with a comb-like structure, and three hydrocarbon surfactants (HS), sodium dodecyl sulfate, SDS, tetradecyl trimethylammonium bromide, DTAB, and t-octylphenoxy polyethoxyethanol, TX-100 in water were investigated using dilute solution phase characteristics, small angle neutron scattering (SANS) and solution viscosity measurements. The surfactants interact with the SS-1 micelles leading to the formation of highly hydrophilic complexes. The enhanced hydrophilicity shifts the unimer ↔ micelle in favor of former. The reduced viscosities of the mixed systems of SS-1—ionic surfactants in the very low SS-1 concentrations were high and show a curvature suggesting strong repulsive interactions among the complexes. The intrinsic viscosity of mixture solutions are more than the SS-1 micellar solutions indicating enhanced hydration. The hydrophilicity increased the cloud points of SS-1 in simple surfactants.

Ultrasonic-thermostatic-assisted cloud point extraction coupled to high-performance liquid chromatography for the analysis of adrenalines residues in milk

A novel approach, ultrasonic-thermostatic-assisted cloud point extraction (US-CPE) combined with high-performance liquid chromatography and ultraviolet detection, is developed for the analysis of adrenalines (beclometasone dipropionate, hydrocortisone butyrate and nandrolone phenylpropionate) in milk samples. It is based on the induction of micellar organized medium by using a non-ionic surfactant TMN-6 (polyether-type organic silicon surfactant; structure: (CH3)3C(CH2)8(OC2H4)XOH; average of X = 6) to extract the target adrenalines. In this experiment, phase diagrams were used to study the cavitation and mass transfer behaviors of the two phases on micelles of TMN-6. The main advantages of this system were that it had no ultraviolet absorption and had higher extraction efficiency. In addition, the phase diagram of US-CPE was determined contrast with ultrasonic-thermostatic-cloud point system. The effects of other operating parameters, e.g., concentration of salt and centrifugation time on extraction of US-CPE system, have also been studied in detail.

Surface Tension and Foam Stability Prediction of Polydimethylsiloxane-Polyol Systems

The Gibbs elasticity modulus represents an important tool to predict the foamability for transient and permanent foams like polyurethane flexible systems. Elasticity is related to foamability and so is used as a synonymous for the purpose of this paper. In this article we propose a method and a thermodynamic model to analyze the espumability of silicone surfactants in polyol binary mixtures using surface tension data. The present work describes foamability through the Gibbs elasticity modulus expressed in terms of first and second derivatives of surface pressure vs bulk composition. Furthermore, the Gibbs adsorption equation and the corresponding novel surface equation of state based on a modification of the Langmuir isotherm resulted in an elasticity equation with analytical solution. It is shown that according to foam model systems of surfactant solution in polyol used at commercial processes, optimum concentration level of surfactant obtained at this article by Gibbs adsorption equation and maximus on elasticity modulus finally match.

Morphology‐Controlled Synthesis of Poly(oxyethylene)silicone or Alkylsilicone Surfactants with Explicit, Atomically Defined, Branched, Hydrophobic Tails

Silicone surfactants are widely used in commerce because of the unusual surface activity when compared with fluorocarbon or hydrocarbon surfactants. However, most silicone surfactants are comprised of ill-defined mixtures, which preclude the development of an understanding of structure-surface activity relationships. Herein, we report a synthetic strategy that permits exquisite control over silicone structure by using the B(C(6)F(5))(3)-catalyzed condensation of hydro- and alkoxysilanes. Six different, precise hydrophobes were then mated to hydrophilic poly(oxyethylene)s of three different molecular weights by a metal-free click cyclization to generate a library of explicit silicone surfactants. These compounds were calculated to have a relatively linear value range of the hydrophilic-lipophilic balance, ranging from about 8 to about 15. The solubility of some of the compounds was too low to measure a critical micelle concentration (CMC). The others exhibited a broad range of surface tension values at the CMC that depend both on the length of the hydrophilic tail and, more importantly, the nature of the hydrophobic head group. Subtle distinctions in surfactant-related properties, which can be attributed to the three-dimensional structures, can be seen for compounds with comparable numbers of hydrocarbons and silicon groups.

NSGA-II-RJG applied to multi-objective optimization of polymeric nanoparticles synthesis with silicone surfactants

AbstractPolydimethylsiloxane nanoparticles were obtained by nanoprecipitation, using a siloxane surfactant as stabilizer. Two neural networks and a genetic algorithm were used to optimize this process, by minimizing the particle diameter and the polydispersity, finding in this way the optimum values for surfactant and polymer concentrations, and storage temperature. In order to improve the performance of the non-dominated sorting genetic algorithm, NSGA-II, a genetic operator was introduced in this study — the transposition operator — “real jumping genes”, resulting NSGA-II-RJG. It was implemented in original software and was applied to the multi-objective optimization of the polymeric nanoparticles synthesis with silicone surfactants. The multi-objective function of the algorithm included two fitness functions. One fitness function was calculated with a neural network modelling the variation of the particle diameter on the surfactant concentration, polymer concentration, and storage temperature, and the other was computed by a neural network modelling the dependence of polydispersity index on surfactant and polymer concentrations. The performance of the software program that implemented NSGA-II-RJG was highlighted by comparing it with the software implementation of NSGA-II. The results obtained from simulations showed that NSGA-II-RJG is able to find non-dominated solutions with a greater diversity and a faster convergence time than NSGA-II.

The characterisation of the interfacial chemistry of adhesion of rigid polyurethane foam to aluminium

The interfacial interactions between a rigid polyurethane foam (RPUF) and aluminium have been studied to understand the mechanisms of adhesion. Three different blowing systems are used in the production of the foam: chemical blowing, physical blowing and a mix of chemical and physical blowing systems. In addition an unfoamed system has been examined for comparison of the catalysts behaviour with and without blowing agents and the surfactant. Peeled failure surfaces have been examined by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF–SIMS). To examine the intact interfacial regions of the RPUFs cured against aluminium, samples have been sectioned by microtomy. The failure surfaces of the aluminium sides exhibit relatively clean aluminium surfaces with RPUF residues observed for all three foamed systems; such thin RPUF layers (ca. 1 nm) indicate good adhesion (and a cohesive failure) between foam and substrate and that the interfacial adhesion is higher than the cohesive strength of the foam. The unfoamed system behaves in a similar manner but has a higher peel strength. A fragment indicative of covalent bond formation between isocyanate and aluminium (nominal mass at 102 u: AlCHNO3 −) is observed on the failure surface of aluminium side, where RPUF/aluminium interface region is present, for all foams. The catalyst used in these formulations, pentamethyldiethylenetriamine (PMDETA), is concentrated at the interface area. Whilst examination of the sectioned specimens shows that the silicone surfactant is concentrated within the cell area fulfilling its role on cell formation and stabilisation, and is not segregated at the RPUF/aluminium interface.

Carbohydrate‐Modified Silicone Surfactants

AbstractSilicone surfactants have been widely used in our daily life and many industrial fields on the basis of their unusual properties. Only in the past decades has the use of silicone as a hydrophobic building block for the preparation of surfactants become common. The recent trend to combine silicone, polyoxyalkylene and carbohydrate moieties in the same molecule has resulted in a plethora of new compounds with new properties. The generic structure and surface activity of silicone surfactants are reviewed in this article. Especially, the preparation, properties and application of carbohydrate‐modified silicone surfactants such as glucosamide‐containing and glycoside‐containing silicone surfactants are described in detail. In addition, the future development of silicone surfactants is discussed.

Silicon-compound coating for preparation of water repellent cotton fabric by admicellar polymerization

Admicellar polymerization of two silicon compounds, methacryloxymethyltrimethylsilane (MSi) and methacryloxypropylpentamethyldisiloxane (MDSi) was investigated using two silicone surfactants, a nonionic and a cationic. Adsorption of the cationic surfactant on cotton was found to be higher than that of the nonionic surfactant. The polymer film on the surface was characterized by SEM, FTIR and XPS and the results showed that a thin polymer coating was successfully formed. The treated fabrics showed good water repellency as determined by contact angle measurement and the MSi-treated cotton showed better water repellency than the MDSi-treated cotton in terms of wetting time.

Herding surfactants to contract and thicken oil spills in pack ice for in situ burning

Abstract In situ burning is an oil spill response option particularly suited to remote, ice-covered waters. The key to effective in situ burning is thick oil slicks. If ice concentrations are high, the ice can limit oil spreading and keep slicks thick enough to burn. In drift ice conditions and open water, oil spills can rapidly spread to become too thin to ignite. Fire-resistant booms can collect and keep slicks thick in open water; however, even light ice conditions make using booms challenging. A multi-year research project was initiated to study oil-herding surfactants as an alternative to booms for thickening slicks in light ice conditions for in situ burning. Small-scale laboratory experiments were completed in 2003 and 2005 to examine the idea of using herding agents to thicken oil slicks among loose pack ice for the purpose of in situ burning. Encouraging results prompted further mid-scale testing in 2006 and 2007 at the US Army Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, NH; at Ohmsett, the National Oil Spill Response Research & Renewable Energy Test Facility in Leonardo, NJ; and, at the Fire Training Grounds in Prudhoe Bay, AK. The non-proprietary hydrocarbon-based herder formulation used in these experiments proved effective in considerably contracting oil slicks in brash and slush ice concentrations of up to 70% coverage. Slicks in excess of 3 mm thick, the minimum required for ignition of weathered crude oil on water, were routinely achieved. Herded slicks were ignited, and burned equally well in both brash and slush ice conditions at air temperatures as low as − 17 °C. The burn efficiencies measured for the herded slicks were only slightly less than the theoretical maximums achievable for equivalent-sized, physically contained slicks on open water. Successful meso-scale field trials of the technique were carried out in the Barents Sea off Svalbard in the spring of 2008 as one facet of a large joint industry project on oil spill response in ice co-ordinated by SINTEF. The larger field experiment involved the release of 630 L of fresh Heidrun crude onto water in a large lead. The free-drifting oil was allowed to spread for 15 min until it was far too thin to ignite (0.4 mm), and then the hydrocarbon-based herder was applied around the slick periphery. The slick contracted and thickened for approximately 10 min at which time the upwind end was ignited. A 9-minute long burn ensued that consumed an estimated 90% of the oil. From 2007 to 2009 experiments were carried out in the laboratory and at CRREL comparing the efficacy of herding agents formulated with silicone-based surfactants, herding agents formulated with second-generation fluorosurfactants, and the hydrocarbon-based herder. The results showed that the fluorosurfactant-based herders did not function better than the hydrocarbon-based herder; however, the new silicone surfactant formulations considerably outperformed the hydrocarbon-based herder. Most recently, experiments were conducted to determine if herding agents could: 1) improve skimming of spilled oil in drift ice; 2) clear oil from salt marshes; and, 3) improve the efficiency of dispersant application operations.

Effect of non-electrolyte additives on micellization and clouding behavior of silicone surfactant in aqueous solutions

In this paper the effects of 26 non electrolyte additives (including 12 alcohols, 7 glycols and 7 amides) on the association and clouding behavior of silicone surfactants (SS) in aqueous solutions have been studied. The results show that the addition of the polar organic liquid additives which are miscible with water increases the critical micelle concentrations (CMC) and cloud point of the SS, whereas the addition of the polar organic liquid additives which are partially soluble in water decreases the CMC and cloud point of SS. The change in Gibbs free energy of micellization in the presence of additives was obtained from the data on critical micelle concentrations. The influence of given additive on the micellization of SS was monitored from the changes in the free energy of micellization values for the surfactant solutions in water and water + additives. For additives belonging to a particular homologous series the effect on the cloud point and micellization is correlated to the length of the hydrophobic alkyl chain.